1. Field of The Invention
The present invention relates generally to a video camera. Particularly, the invention relates to a video camera which is lightweight and compact.
2. Description of The Prior Art
Video cameras are widely used in industry and by various people privately and professionally. In order to increase the variety of uses for such video cameras and for increasing the portability and convenience thereof, it has been required for various reasons to provide a video camera which is light in weight and small in size and which uses a reduced number of parts.
FIG. 5 shows a cross sectional view of a front side of a conventional video camera, while FIG. 6 shows an exploded perspective view thereof. As may be seen from FIGS. 5 and 6, a video camera 50 includes a box-shaped casing 51 and a front panel 52. In a center portion of the front panel 52 a lens mounting opening 53 is formed. A movement enabling ring 54 fits around an outer circumference of the lens mounting opening 53 while an adjusting ring 55 fits around an outer circumference of the movement enabling ring 54, as best seen in FIG. 5. At an outer circumference of the movement enabling ring 54 and all inner circumference of the adjusting ring 55, threaded portions 54a and 55a are respectively formed for allowing the movement enabling ring 54 and the adjusting ring 55 to rotatably engage in screw-like fashion. Further, in the axial direction of the movement enabling ring 54 a longitudinal groove 54b is formed. The longitudinal groove 54b receives a projecting portion 57a of a push plate 57, as seen in FIG. 6. The adjusting ring 55 is movable in the axial direction thereof according to movement of the push plate 57.
Also, as seen in the drawings, according to such conventional video camera construction an optical filter 58 is provided. Referring to FIG. 5, a mediating member 59 is disposed around the optical filter 58 for spacing the optical filter 58 from an image pickup device 60, such as a CCD or the like. The optical filter 58, the mediating member 59 and the image pickup device 60 are retained in an installation member 61 which is attached to a metal plate 62. The metal plate 62 is provided with two cylindrical openings 62a, 62a which respectively receive guide rods 63, 63 therethrough. Forward ends of the guide rods 63, 63 are anchored in the rear face of the front panel 52. The rearward ends of the guide rods 63, 63 are secured by nuts 64, 64 at the rear side of the metal plate 62 and coil springs 65, 65 are interposed between the rear side of the metal plate 62 and the nuts 64, 64, one of the coil springs 65 being disposed around one of the guide rods 63 respectively. Thus, due to the spring force of the coil springs 65, 65 the metal plate 62, the installation member 61, the push plate 57 and the adjusting ring 55 are collectively biased in the axially forward direction toward the movement enabling ring 54 to place pressure thereon.
According to this construction, the rotatable adjusting ring 55 is engaged with the movement enabling ring 54 via the threaded portions 55a and 54a. The adjusting ring 55 is movable in the axial direction according to rotation thereof along tile movement enabling ring 54 to limits determined by the pitch of the threaded portions 55a and 55b. According to the movement of the adjusting ring 55, the compression force of the coil springs 65 received by the installation member 61 is active to change the axial position thereof for moving the image pickup device 60. According to this, a `flangeback` distance L may be adjusted between a standard lens mounting position P1 and a position P2 of the image pickup device 60.
According to such conventional construction, a mechanism for effecting flangeback adjustment becomes complex. A number of parts required is high and assembly and parts costs are increased. In addition reliability is more difficult to assure for such a complex mechanism. Also, since a certain distance (L) is required between the image pickup device 60 and the front panel due to the number of structural components, a CS mount design, which may accommodate the mechanism and shorten the distance L, is difficult to implement and an overall size of the video camera tends to be increased.
Thus it has been required to provide a lightweight, compact video camera with simplified mechanical structure.